Weakly coordinating counter-ions for highly efficient catalysis of intramolecular hydroamination

Serin L. Dabb, Joanne H H Ho, Richard Hodgson, Barbara A. Messerle, Jörg Wagler

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

Abstract

A series of cationic rhodium(i) and iridium(i) complexes of the type [M(LL)(C2)]BArF 24 (where M = Rh or Ir, LL = bis(pyrazol-1-yl)methane (bpm), bis(N-methylimidazol-2-yl)methane (bim) or 1-(2-(diphenylphosphino)ethyl)-3,5- diphenylpyrazole (Ph2PyP), C2 = 1,5-cyclooctadiene (COD) or (CO)2 and BArF 24 = tetrakis[3,5- bis(trifluoromethyl)phenyl]borate) were synthesised in good yields. The solid-state structure of a number of complexes, including [Ir(Ph 2PyP)(COD)]BArF 24, [Ir(bpm)(COD)]BAr F 24 and [Ir(bim)(COD)]BArF 24 was determined using X-ray crystallography. The efficiency of the complexes as catalysts for the intramolecular hydroamination of 4-phenyl-3-butyn-1-amine, 4-pentyn-1-amine and 2-(2-phenylethynyl)aniline was established. The incorporation of the BArF 24 - counter-ion in the Rh(i) and Ir(i) complexes was found to significantly improve the catalytic activity of the complexes, compared to the analogous Rh(i) and Ir(i) complexes containing BPh4 - as the counter-ion. Excellent conversions were achieved for the cyclisation of 2-(2-phenylethynyl)aniline to 2-phenylindole using [Rh(bpm)(CO)2]BArF 24 as a catalyst. The use of a microwave reactor for enhancing the catalysed reactions was also investigated.

Original languageEnglish
Pages (from-to)634-642
Number of pages9
JournalDalton Transactions
Issue number4
DOIs
Publication statusPublished - 2009
Externally publishedYes

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